1. Field of the Invention
The present invention relates to a capping apparatus, in particular for capping containers with crown caps.
2. Description of the Related Art
In the sector of closing containers with crown caps, the Applicant has already used for years a capping system which involves traditional side feeding of the crown caps, which are attracted by a magnet mounted on the bottom of a first piston sliding inside a second it piston.
The second piston is shaped at the bottom so as to form a chamber with a conical or cylindrical recess, inside which centering of the cap occurs when the two pistons descend onto the container, which is supported by a fixed plate.
Basically both pistons descend initially onto the container; then, when the first piston or internal piston encounters the mouth of the container it stops, pressing against it and centering the cap, while the second piston or external piston continues its descending movement so as to perform fastening of the cap onto the mouth of the container. Means are provided in order to compensate for slight variations in height of the containers, of the order of about xc2x17 mm.
EP 0470360 also discloses a capping device for crown caps in which there is an internal piston containing a magnet and sliding together with an external piston during a first descending step, followed by a second step in which the internal piston remains at a standstill against the bottle, while the external piston continues further the downward movement, embracing the cap and the mouth of the bottle.
Both in the solution of the Applicant and in that of the aforementioned document, centering of the cap is performed in the presence of the container, and the container is supported by a plate or by a fixed surface.
A drawback of these constructional designs consists in the fact that if the bottle is not perfectly centered with respect to the conical recess (also called capping die) or if the crown cap is not perfectly centered on the magnetic piston, incorrect application of the cap may occur.
A further drawback consists in the fact that the axis of the container during capping coincides with the axis of the capping pistons and therefore in the case of lubricant escaping from the pistons, this may contaminate the container.
The latter drawback has, moreover, been solved by a capping device in which the bottle is axially displaced with respect to the capping pistons, on which the conical recess and the magnet support are mounted in cantilever fashion. The bottle rests on a fixed plate and the capping pistons are positioned below the bottle capping zone in an area of the machine which greatly limits the accessibility thereof, complicating the maintenance operations.
The object of the present invention is to eliminate the abovementioned drawbacks and provide a capping apparatus which allows pre-centering of the cap to be performed without the presence of the bottle.
Said objects are fully achieved by the capping machine forming the subject of the present invention, which is characterized by the contents of the claims below.
The capping machine comprises a first movable element coaxial with the capping axis and carrying at the bottom a magnet for attracting a cap; a second movable element coaxial with the capping axis and sliding outside the first movable element, together therewith and with respect thereto; means, which are eccentric with respect to the capping axis, for actuating the first and the second movable element; and is characterized in that said means are positioned at a higher level than the container capping zone.
Said means consist of a first piston and a second piston which are coaxial with one another and connected to the first and second movable element by means of arms.